Host modification of a bacterial quorum-sensing signal induces a phenotypic switch in bacterial symbionts

Specific bacterial communities colonize epithelial surfaces of most animals. In the last years many host mechanisms that control bacterial community composition have been identified. In contrast, only a few mechanisms are known that allow the host to target the behavior of its bacterial colonizers. We identified a eukaryotic mechanism based on an oxidoreductase activity, which enables the cnidarian Hydra to modify bacterial quorum-sensing (QS) molecules. The modification of QS signals leads to a phenotypic switch in the bacterial symbionts and promotes colonization of host tissue.